1. Field of the Invention
The present invention relates to an automatic fire protection sprinkler, and in particular an extended coverage, storage sprinkler, designed in accordance with density/area criteria.
2. Related Art
Fire protection sprinklers conventionally are connected to a conduit to receive pressurized fire-extinguishing fluid, such as water. A typical sprinkler has a base with a threaded portion for connection to the conduit and an output orifice to output the fluid to provide fire control and/or suppression. The output orifice is sealed by a seal cap, which is held in place by a release mechanism. The release mechanism is designed to release the cap under predetermined conditions, thereby initiating the flow of fire-extinguishing fluid. A typical release mechanism includes a thermally-responsive element, e.g., a frangible bulb or fusible link, and may also include a latching mechanism.
Certain conventional sprinklers have a pair of arms that extend from the base portion and meet at a hub portion to form a frame. The hub portion is spaced apart from the output orifice of the base portion and is aligned with a longitudinal axis thereof. The hub portion may have a set-screw configured to apply a pre-tension force to the release mechanism. A deflector may be mounted on the hub, transverse to the output orifice, to provide dispersion of the output fluid.
Fire protection sprinklers may be mounted on a fluid conduit running along a ceiling and may either depend downward from the conduit, which is referred to as a “pendent” configuration, or may extend upward, which is referred to as an “upright” configuration. Alternatively, a sprinkler may be mounted on a wall, a certain distance below the ceiling, which is referred to as a “horizontal sidewall” configuration. Horizontal sidewall sprinklers have an output orifice that is oriented so that the fluid is output horizontally and sprays onto an area to be protected in front of the sprinkler.
An “extended coverage storage sprinkler (density/area),” as described in Section 5.11 of UL 199 (“Standard for Automatic Sprinklers for Fire-Protection Service,” Underwriters' Laboratories, 11th Ed., Nov. 4, 2005) is a sprinkler that is intended to be installed using the extended coverage area (e.g., 14 ft by 14 ft) and density/area criteria specified in NFPA 13 (“Standard for the Installation of Sprinkler Systems,” National Fire Protection Association, Inc., 2002 Edition). These sprinklers incorporate a heat responsive element and release mechanism that has a response time equal to or less than a standard response sprinkler used on sprinklers designed for standard spacings (e.g., 12 ft by 12 ft).
NFPA 13 defines a number of different types of storage sprinklers. Section 12.7.2, for example, provides “Sprinkler Design Criteria for Storage and Display of Class I through Class IV Commodities, Cartoned Non-Expanded Group A Plastics, and Non-Expanded Exposed Group A Plastics in Retail Stores.” In such applications, the sprinkler must be connected to a wet pipe system designed to meet two separate design points: 0.6 gpm/ft2 density over 2000 ft2 and 0.7 gpm/ft2 density for the four hydraulically most demanding sprinklers (e.g., the four sprinklers furthest from the source). Systems meeting these density/area criteria are permitted for use in protecting single and double-row slatted shelf racks using an extended coverage sprinkler with a nominal K-factor of 25.2 listed for storage occupancies.